This invention concerns glycidyl methacrylate (GMA) polymer, copolymers of GMA and other methacrylate esters, solvolysis products of the GMA-containing polymers and a process for preparing said polymers.
Free-radical polymerization of GMA is known. The products, however, are not uniform with respect to molecular weight distribution with molecular weight being, in addition, difficult to control. Furthermore, in the case of block copolymerization, the block lengths of GMA are highly variant and, by the very nature of radically-induced systems, some GMA is inevitably incorporated randomly rather than in block fashion. For example, see "Block Copolymers", Noshay et al, Academic Press, New York, 1977, page 31.
There are literature reports that GMA can be anionically polymerized with simple alkyllithium reagents such as n-butyllithium: Arbuzova et al., Vysokomol. Soyed., 5, 1819 (1963), CA 60/6932g; Iwakura et al., Polymer Letters, 5, 29 (1967), CA 66 65877y; and Ito et al., Polymer Journal, 1, 278 (1970); CA 73/45909b. Contrary to such reports, Comparative Examples A to E hereafter demonstrate that GMA cannot be polymerized employing n-butyllithium (at low temperature in tetrahydrofuran).
U.S. Pat. No. 4,048,421, in Example VII, describes the anionic copolymerization of styrene and glycidyl methacrylate. There, the initiating species is an organic derivative of an alkali metal aluminum hydride. Patentees characterize the products as having broad molecular weight distributions; see, for instance, column 4, lines 38 to 43.
Anionic 1,1-diphenylhexyllithium (DPHLi) is known as an initiator for MMA to form essentially monodisperse polymers. However, DPHLi does not of itself initiate polymerization of GMA to give polymers of predictable and uniform composition. See Comparative Example F hereafter which was designed, using THF solvent at -78.degree. C., to produce a polymer with M.sub.n of 4200. However, the product had a M.sub.n of 24,000 and a broad molecular weight distribution (M.sub.w /M.sub.n of 1.86). The discrepancy in the M.sub.n 's corresponded to destruction of about 83% of the initiator leaving only 17% of the living ends originally provided for. This untoward result occurred because the relatively highly nucleophilic diphenylhexyl anion reacted with the epoxide ring of GMA to form a non-initiating alkoxide species with insufficient opportunity for "living" chain propagation to occur.